As I mentioned before don't limit yourself in creating a good deep cycling bank for yourself. The options are almost limitless and even 2V batteries, such as those by Rolls/Surrette are available, These large heavy 2V cells are a true 15+ year battery and are the true Kings of the deep cycle world.
Here we are looking as a SERIES/PARALLEL configuration of four 6V 230Ah GC2 batteries. This yields an effective bank size, in a series/parallel configuration of 460Ah's at 12V.
SERIES:
When you connect two 6V DC batteries in series, negative terminal of battery #1 to positive terminal of battery #2 you've now created a single 12V deep cycle battery.
12V batteries are nothing more than 6 series-wired cells inside a single plastic case. A 6V battery is three series wired cells inside a single plastic case. All you are doing for a 12V bank using 6V batteries is wiring them externally in series.
In SERIES wiring of 6V batteries we ADD VOLTAGE but AMP HOUR capacity stays the same.
SERIES 6V + 6V = 12V
Two 230Ah Batteries In Series = 230Ah's
PARALLEL:
In Parallel wiring we add AMP HOURS but VOLTAGE stays the same.
PARALLEL 12V + 12V = 12V or 6V+6V = 6V
Two 230Ah Batteries In Parallel = 460Ah's
SERIES/PARALLEL:
In series parallel (pictured) we wire in series first, to attain desired voltage, then we wire in parallel to gain capacity.
This bank consists of two series wired banks to attain 12V each. These series banks were then paralleled to created a 460Ah house bank.
While these take off points from the series parallel bank will work, and give you 12V, it is less than ideal. Every battery manufacturer I know of advises against wiring a series parallel bank in this manner.
Don't Just Take My Word For It
EnerSys, the inventors of the Odyssey TPPL AGM battery as well as the inventors of the Optima battery, and the leaders in standby back up systems, military applications and other industrial battery applications spells out correct parallel wiring better than I can. When you are wiring series banks in parallel this applies!
Quote = Odyssey/Enersys:
"Parallel Connections
It is common to have batteries connected in parallel to
achieve a desired amp-hour capacity. This is done by
connecting all the positives to each other and all the
negatives to each other.
Typically the positive and negative leads to the load
are taken from the same battery; usually the leads from
the first battery are used. This is not a good practice.
Instead, a better technique to connect the load is to take
the positive lead from one end of the pack (the first or last
battery) and the negative lead from the other end of the pack.
The two methods are illustrated above. Solid lines and
arrows indicate positive terminals and leads; broken lines
and arrows indicate negative terminals and leads.
In both illustrations, the positive leads are connected to
each other; similarly the negative leads are connected to
each other. The only difference is that in the first illustration
the positive and negative leads to the load come from the
first and last batteries. In the second case, both leads to
the load are tapped from the same battery.
The first schematic is recommended whenever batteries
are hooked up in parallel to increase battery capacity.
With this wiring, all batteries are forced to share both charge
and discharge currents. In contrast, a closer inspection
of the second schematic shows that it is possible for only
the battery whose terminals are tapped to support the load.
Implementing the first schematic eliminates this possibility
and is therefore a better one."
Trojan Parallel Takes Offs
Here is Trojan's diagram. This information is out there and easy to find, but from what I see on boats, it is not widely looked at. Battery life in the real world is a complex puzzle. All the small pieces need to fit for the best cycle life..! Wiring your bank, as it should be, is one of those small puzzle pieces...
Series Parallel = Correct
When wiring a bank for series / parallel you will first want to fit and orient the batteries as they will be physically installed on the boat. You then construct the series jumpers and wire them.
Once you've created your series 12V banks you can then wire them in parallel. As explained above, by EnerSys/Odyssey Battery, it is important that the loads and all charging input be wired from opposite ends or corners of the bank, as shown, to help keep it in balance throughout its life.
With a series parallel set up the ONLY TERMINALS you connect the boat to are those two corners. You do not want to "center tap" with a 6V series or series/parallel bank otherwise you may not have a 12V bank for that circuit..
Final Thoughts:
Can 12V Group 24, 27, 31, 4D & 8D flooded batteries work? Sure, absolutely, and they do in the tens of thousands on boats every day.
The question here is of value and are you getting what you paid for on the sticker, or were sold, when you bought what you thought was a deep cycle battery? When a 12V flooded marine battery is sold for more money and with half the rated lab cycles my answer = no.
When purchasing house bank deep cycling batteries always consider cycle life in the equation. This is the part most everyone buying batteries forgets or entirely leaves out of the decision making process. The battery buying process is not just about Amp Hours and $$$. It is Ah's, $$$ and cycle life when you are buying deep cycle batteries.
By labeling "light cycling" batteries as deep cycle it's the battery maker who wins because you'll buy more batteries in a shorter period of time. By doing your home work you can avoid getting bitten by the muddy and misleading marketing of light cycling batteries.
MAY-2006
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